feat: gear registry — manage bikes/shoes per athlete, set per activity

- New /api/gear CRUD endpoints (gear.json per user)
- Gear tab in AthleteView (owner-only): add, edit, retire items
- EditDrawer gear field becomes a dropdown when registry has items
- Strava API sync now resolves gear_id → name, adds to registry automatically
- Strava ZIP import reads Gear column from activities.csv
- POST /api/strava/import-gear for one-time backfill from stored originals

bincio/serve/server.py

@@ -23,6 +23,7 @@ from bincio.serve.routers import (
     download,
     feed,
     garmin,
+    gear,
     ideas,
     me,
     ogimage,
@@ -69,5 +70,6 @@ for _router in [
     garmin.router,
     ideas.router,
     ogimage.router,
+    gear.router,
 ]:
     app.include_router(_router)